Implantable medical devices, such as pacemakers, defibrillators, brain stimulators, pain relief stimulators, sleep apnea stimulators, other stimulation devices and the like, require a source of power to function and operate. The source of power is usually a battery which is commonly contained in a can together with electronic components. The can is usually attached to another part of the implantable medical device which delivers some kind of therapy to a patient based on electrical impulses. As such devices may be typically worn or carried by patients for years or even decades the battery is usually implanted in the patient as part of the implantable medical device and is typically integrated into the device and not removable. When the battery dies and needs replacement, the patient must undergo surgery to remove the battery and replace it with a new one. In some devices, the entire device needs to be replaced as the battery is not a separately replaceable component. Thus the entire medical device requires replacement at the time of battery depletion. State of the art batteries used in such devices may last anywhere up to 5-7 years. However a patient who receives a pacemaker or defibrillator early in his or her life, such at age 40, and lives into his 80s may have to undergo multiple surgeries just to replace the battery of his pacemaker or defibrillator.
In many implantable medical devices, a part of the device, such as an electrical lead, may be positioned apart from the can containing the battery and electronics accordingly. For example, in prior art pacemakers, electrical leads which are used to both measure the heart's electrical activity and also provide electrical stimulation to the heart are placed in a different location than the can which houses the battery as well as electronics for controlling the pacemaker. The electrical leads are usually positioned within the heart, whereas the can may be positioned under the collarbone. Implanting the pacemaker requires major surgery as the electrical leads need to be positioned within the heart of a patient. In addition, an incision needs to be made to position the can in the body of the patient. At period intervals typically ranging from 5 to 7 years, the patient will have to undergo surgery to enable access to the can where the old battery is. The can is then replaced by removing it and inserting a new can, containing a new battery, in the patient. In addition, if any issues or problems ever occur with the electrical leads, the patient will again have to undergo major surgery to fix, repair or replace the electrical leads within the heart. It is noted that removing old electrical leads from the heart may be a complex medical procedure which can cause additional complications. In some cases, the old electrical leads may be left in the heart and new electrical leads are implanted next to the old ones. The can, which in prior art pacemakers is substantially bulky, is usually positioned in the body such that the patient will not be impaired with regard to physical movement and also to reduce any discomfort in the patient due to the positioning of the can. The patient though may suffer from discomfort in the tissue area that surrounds the can if a significant force is placed on the area, such as by getting hit in the area or falling on the area. In addition, thin patients or patients with limited amounts of subcutaneous tissue may also risk erosion of the device, for example the can, through the skin.
The integration of the power source with the other parts of an implantable medical device, such as the electrical leads, into a single unit in order that the can does not need to be separated from the electrical leads would make such an implantable medical device easier to handle and would simplify the surgery required to insert and remove the device in a patient. Such a unit could also include at least one electronic circuit or a series of electronic circuits as well as at least one capacitor. However replacing the battery of such a device every few years would still require the patient to undergo surgery. Such a device is described in U.S. Pat. No. 7,985,500 to Root et al., entitled “Method and apparatus for flexible battery for implantable device,” which is directed to an apparatus for storing energy, the apparatus having a first portion comprising a flexible substrate containing a polymer electrolyte and a second portion adapted to provide a conformable housing surrounding the first portion. The apparatus is adapted to provide a source of energy to an implantable device. The apparatus with the implantable device forms a flexible implantable device capable of traversing the circulatory system of a body with minimal obstruction of flow within the circulatory system. In other embodiments of the apparatus to Root, the apparatus comprises at least one single cell contained within a flexible housing. Such an apparatus is adaptable to provide a source of energy to an implantable device. The apparatus can also contain both a sensor and a power source within the flexible housing. The housing can include an anchoring mechanism for anchoring the device during implantation within the body. The apparatus can also include a series of smaller battery cells attached by flexible conductive interconnects that are further contained within the conformable housing capable of traversing the circulatory system of the body.
What is needed then is an implantable medical device having a structure that incorporates the power source and electronic components, thus simplifying its placement in a patient, yet which also allows the power source to be easily replaced requiring only minor, less-invasive surgery. In addition, such a device should not impair a patient's movement at all and should cause no discomfort to the patient during their daily routine and activities.